Question Video: Identifying Why Solutions Are Placed in a Water Bath before Performing a Calorimetry Experiment | Nagwa Question Video: Identifying Why Solutions Are Placed in a Water Bath before Performing a Calorimetry Experiment | Nagwa

Question Video: Identifying Why Solutions Are Placed in a Water Bath before Performing a Calorimetry Experiment Chemistry • First Year of Secondary School

A student is setting up an experiment to measure the enthalpy change in a neutralization reaction between hydrochloric acid and potassium hydroxide. Before mixing the two solutions together in a polystyrene cup, the student places a beaker of each solution in a water bath set to 25°C. Why does the student do this?

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Video Transcript

A student is setting up an experiment to measure the enthalpy change in a neutralization reaction between hydrochloric acid and potassium hydroxide. Before mixing the two solutions together in a polystyrene cup, the student places a beaker of each solution in a water bath set to 25 degrees Celsius. Why does the student do this? (A) To increase the rate of reaction between the hydrochloric acid and the potassium hydroxide. (B) To remove any impurities in the solutions. (C) To ensure the reactants have the correct activation energy needed to react. (D) To ensure both solutions are at the same temperature as each other. (E) To make the solutions less viscous.

The question describes an experiment used to measure the enthalpy change of the neutralization reaction between hydrochloric acid and potassium hydroxide. This type of experiment is a calorimetry experiment. A calorimetry experiment can be used to measure the heat energy change or enthalpy change taking place in a reaction. To perform a calorimetry experiment, we need a calorimeter, an insulated reaction vessel. We can construct a basic calorimeter by simply using a polystyrene cup with a lid. The solutions being reacted are added to the calorimeter, and the temperature is monitored with a thermometer.

When the reaction takes place, heat energy is either absorbed or released. This results in a change in temperature. We can then relate the observed change in temperature to the change in heat or the enthalpy change. Because we use the change in temperature to determine the enthalpy change, it’s important that this temperature change is only due to the reaction taking place. We know that if we mix a hot solution with a cold solution, the temperature will change. This temperature change is due to the transfer of kinetic energy from the molecules in the hot solution to the molecules in the cold solution.

In this question, the goal of the experiment was to measure the enthalpy change of a reaction. If the temperature of the two solutions used in the experiment is different, then the temperature change is due not only to the reaction, but also the kinetic energy transfer between the different temperature solutions. This is why the student places a beaker of each of the solutions in a water bath before performing the experiment. By doing this, the student ensures that each of the solutions is at the same temperature and that the resulting temperature change when the solutions are combined is only due to the heat absorbed or released during the reaction.

Therefore, the reason why the student places a beaker of each solution in a water bath before mixing the solutions together is answer choice (D): to ensure both solutions are at the same temperature as each other.

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